Imaging lens device and imaging apparatus

ABSTRACT

An imaging apparatus and imaging lens device comprises a light path folding optical system having a reflector that folds the optical axis incident perpendicular to the gravitational direction toward the gravitational direction. An imaging element converts an image formed by the light path folding optical system into an electrical signal. A drive unit moves a shake correction lens group including at least one lens in the direction perpendicular to a vertical optical axis, the vertical optical axis being folded toward the gravitational direction by the reflector, wherein the shake correction lens group is moved in the direction perpendicular to the vertical optical axis to move the image in the direction perpendicular to the vertical optical axis.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/491,081, filed on Jul. 24, 2006, and claims priority to JapanesePatent Application JP 2005-217288 filed in the Japanese Patent Office onJul. 27, 2005, the entire contents each of which being incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel imaging lens device and imagingapparatus. The invention particularly relates to an imaging lens devicethat is of compact design and has an anti-vibration capability ofcorrecting image-shake due to unpredictable vibration with less powerconsumption so that it is suitable for an imaging lens device fordigital input/output equipment, such as digital still cameras anddigital video camcorders.

2. Description of the Related Art

In recent years, imaging apparatus using a solid-state imaging element,such as digital still cameras, have become commonplace. Among others, inthe case of digital still cameras and the like, it is desired to developan imaging lens having excellent imaging performance that matches with amegapixel solid-state imaging element. A strong need also exists for acompact, in particular, slim lens. Imaging lenses in which compactdesign of the lens is achieved by decreasing the distance between thepixels to reduce the size of the imaging element, and slim design of thelens is achieved by employing a light path folding optical system havebecome commonplace.

For example, the optical system described in JP-A-2000-131610 achievesslim design in the direction of the optical axis of incoming light byusing a reflective member while maintaining high imaging performance.However, an imaging apparatus employing such a light path foldingoptical system is much more susceptible to hand-shake during imageacquisition due to the resultant compact and slim design of theapparatus together with higher resolution and compact design of theimaging element. Accordingly, there exists an increased demand to add ahand-shake correction capability.

On the other hand, Japanese Patent No. 3359131 proposes an opticalsystem having an anti-vibration capability in which a shake correctionlens group is shifted in the direction perpendicular to the opticalaxis.

SUMMARY OF THE INVENTION

However, the optical system described in Japanese Patent No. 3359131 hasa problem because it is configured such that the shake correction lensgroup is shifted in the direction perpendicular to the optical axisextending horizontally, the shake correction lens group needs to be heldagainst the gravitational force and hence may require a full-timedriving force, resulting in increased power consumption.

In view of the above problems, the invention aims to achieve slim designby employing a light path folding optical system, add a hand-shakecorrection capability, and lower power consumption.

According to one embodiment of the invention, there is provided animaging apparatus and imaging lens device comprises a light path foldingoptical system having a reflector that folds the optical axis incidentperpendicular to the gravitational direction toward the gravitationaldirection. An imaging element converts an image formed by the light pathfolding optical system into an electrical signal. A drive unit moves ashake correction lens group including at least one lens in the directionperpendicular to a vertical optical axis, the vertical optical axisbeing folded toward the gravitational direction by the reflector,wherein the shake correction lens group is moved in the directionperpendicular to the vertical optical axis to move the image in thedirection perpendicular to the vertical optical axis.

According to an embodiment of the invention, there is provided animaging lens device. The imaging lens device includes a light pathfolding optical system having a reflector that folds the optical axisincident perpendicular to the gravitational direction toward thegravitational direction and an imaging element that converts an imageformed by the light path folding optical system into an electricalsignal. The imaging lens device also includes drive means that movessome of lens groups or one lens (hereinafter referred to as “shakecorrection lens group”) in the direction perpendicular to the opticalaxis folded toward the gravitational direction by the reflector(hereinafter referred to as “vertical optical axis”). The imaging lensdevice is configured such that the shake correction lens group is movedin the direction perpendicular to the vertical optical axis to move theimage in the direction perpendicular to the vertical optical axis.

Therefore, in the imaging lens device according to an embodiment of theinvention, the shake correction lens group is supported in thegravitational direction.

An imaging lens device according to another embodiment of the inventionis configured such that the imaging element, instead of the shakecorrection lens group, is moved in the direction perpendicular to thevertical optical axis.

An imaging apparatus according to an embodiment or another embodiment ofthe invention includes the imaging lens device according to theembodiment or the other embodiment of the invention, and furtherincludes hand-shake detection means that detects shake of the imaginglens device and hand-shake correction control means that correctsdisplacement of the imaging position of an object image based on theshake of the imaging lens device detected by the hand-shake detectionmeans. The hand-shake correction control means instructs the drive meansto move the shake correction lens group or the imaging element by anamount and in a direction based on the shake of the imaging lens devicedetected by the hand-shake detection means.

Therefore, the imaging apparatus according to the embodiment or theother embodiment of the invention can correct image-shake due to shakeof the imaging lens device.

An imaging lens device according to an embodiment of the inventionincludes a light path folding optical system having a reflector thatfolds the optical axis incident perpendicular to the gravitationaldirection toward the gravitational direction and an imaging element thatconverts an image formed by the light path folding optical system intoan electrical signal. The imaging lens device also includes drive meansfor moving some of lens groups or one lens (hereinafter referred to as“shake correction lens group”) in the direction perpendicular to theoptical axis folded toward the gravitational direction by the reflector(hereinafter referred to as “vertical optical axis”). The imaging lensdevice is configured such that the shake correction lens group is movedin the direction perpendicular to the vertical optical axis to move theimage in the direction perpendicular to the vertical optical axis.

An imaging lens device according to another embodiment of the inventionincludes a light path folding optical system having a reflector thatfolds the optical axis incident perpendicular to the gravitationaldirection toward the gravitational direction and an imaging element thatconverts an image formed by the light path folding optical system intoan electrical signal. The imaging lens device also includes drive meansthat moves the imaging element in the direction perpendicular to theoptical axis folded toward the gravitational direction by the reflector(hereinafter referred to as “vertical optical axis”).

Therefore, in the imaging lens device according to the embodiment or theother embodiment of the invention, the use of the light path foldingoptical system allows a slim imaging lens device in the incoming opticalaxis direction. Furthermore, the shorter side of the imaging element isoriented to the direction that determines the thickness or the size inthe incoming optical axis direction of the imaging lens device, allowinga slimmer imaging lens device.

In addition to the above, by moving the shake correction lens group orthe imaging element in the direction perpendicular to the verticaloptical axis, image-shake due to hand-shake can be corrected.Furthermore, the shake correction lens group or the imaging element maybe moved in the direction perpendicular to the vertical optical axisonly when hand-shake is to be corrected, while the shake correction lensgroup or the imaging element can be held aligned with the verticaloptical axis only by supporting it in the gravitational direction whenhand-shake correction may not be required. Therefore, unlike theconventional imaging lens device in which the shake correction lensgroup or the like is moved in the direction perpendicular to the opticalaxis extending horizontally, that is, in the vertical direction, verylittle holding electrical power may be required for holding the shakecorrection lens group or the like aligned with the optical axis,allowing decreased power consumption. In particular, to drive the shakecorrection lens group or the imaging element, the gravitational effectis not needed to be taken into account either in the pitch direction(depth direction) or the yaw direction (width direction). Therefore, thedrive means can employ the same mechanism independent of the drivingdirection, allowing the mechanism and circuitry to be easily designed.

In an imaging lens device according to an embodiment of the invention,as the drive means mechanically bears the weight of the shake correctionlens group or the imaging element in the gravitational direction, verylittle electrical power may be required for holding the shake correctionlens group or the imaging element aligned with the vertical opticalaxis.

In an imaging lens device according to another embodiment of theinvention, as the shake correction lens group is fixed in the verticaloptical axis direction, there is no need to provide another drive meansin the proximity of the above-mentioned drive means, thereby preventingan increased diameter of the lens barrel.

In an imaging lens device according to another embodiment of theinvention, as the shake correction lens group is all or part of the lensgroup located closest to the imaging element and satisfies the conditionequation (1) |(1−βa)×βb|<1.8, where βa is the magnification of the shakecorrection lens group and βb is the magnification of the lens grouplocated next to the shake correction lens group and closer to the imageplane, it is possible to correct hand-shake by shifting the shakecorrection lens group by a small amount without having to achieve highprecision in positioning in the vertical optical axis direction.Moreover, all or part of the lens group is assigned as the shakecorrection lens group such that the space between the lens group and theimaging element is relatively large, allowing the drive means to beeasily placed and designed.

In an imaging lens device according to another embodiment of theinvention, the light path folding optical system includes a plurality oflens groups and works as a zoom lens system in which its magnificationchanges when the respective distances between the lens groups change. Asthe reflector is placed in a stationary lens group during zooming, theshake correction lens group or the imaging element can be orientedperpendicular to the gravitational direction and a compact imaging lensdevice can be easily achieved because the lens group accommodating thereflector, which tends to be large, is stationary.

In an imaging lens device according to another embodiment of theinvention, the light path folding optical system includes, in order ofincreasing distance from an object, a first lens group that has positivepower and is stationary during zooming, a second lens group havingnegative power, a third lens group having positive power, a fourth lensgroup having positive power, and a fifth lens group having negativepower. Zooming is performed by moving at least the second and fourthlens groups. The first lens group includes, in order of increasingdistance from an object, a first single lens having negative power, areflector that folds the optical axis incident perpendicular to thegravitational direction by 90 degrees toward the gravitationaldirection, and at least one second lens having positive power. Since thereflector is accommodated in the first lens group that is stationaryduring zooming, a compact imaging lens device can be easily achieved. Asthe shake correction lens group is stationary during zooming andsituated in the fifth lens group that is closest to the imaging elementand may have a space for placing the drive means for shake correction,the drive means will not interfere with other drive means and opticalmembers, allowing the drive means to be easily placed and designed.Additionally, as a positive lens group in the fifth lens group havingnegative power is used as the shake correction lens group, performanceof hand-shake correction can be substantially consistent.

In an imaging lens device according to another embodiment of theinvention, the mechanism of the drive means may not require any holdingelectrical power for holding the shake correction lens group alignedwith the vertical optical axis, allowing decreased power consumption.

An imaging apparatus according to an embodiment of the inventionincludes an imaging lens device having a light path folding opticalsystem and an imaging element that converts an image formed by the lightpath folding optical system into an electrical signal, hand-shakedetection means that detects shake of the imaging lens device, andhand-shake correction control means that corrects displacement of theimaging position of the object image based on the shake of the imaginglens device detected by the hand-shake detection means. The imaging lensdevice includes a reflector that folds the optical axis incidentperpendicular to the gravitational direction toward the gravitationaldirection, and drive means that moves some of lens groups or one lens(hereinafter referred to as “shake correction lens group”) in thedirection perpendicular to the optical axis folded toward thegravitational direction by the reflector (hereinafter referred to as“vertical optical axis”). The imaging lens device is configured suchthat the shake correction lens group is moved in the directionperpendicular to the vertical optical axis to move the image in thedirection perpendicular to the vertical optical axis. The hand-shakecorrection control means instructs the drive means to move the shakecorrection lens group by an amount and in a direction based on the shakeof the imaging lens device detected by the hand-shake detection means.

An imaging apparatus according to another embodiment of the inventionincludes an imaging lens device having a light path folding opticalsystem and an imaging element that converts an image formed by the lightpath folding optical system into an electrical signal, hand-shakedetection means that detects shake of the imaging lens device, andhand-shake correction control means that corrects displacement of theimaging position of the object image based on the shake of the imaginglens device detected by the hand-shake detection means. The imaging lensdevice includes a reflector that folds the optical axis incidentperpendicular to the gravitational direction toward the gravitationaldirection, and drive means for moving the imaging element in thedirection perpendicular to the optical axis folded toward thegravitational direction by the reflector (hereinafter referred to as“vertical optical axis”). The hand-shake correction control meansinstructs the drive means to move the imaging element by an amount andin a direction based on the shake of the imaging lens device detected bythe hand-shake detection means.

Therefore, in the imaging apparatus according to the embodiment and theother embodiment of the invention, the use of the light path foldingoptical system allows a compact imaging apparatus in the incomingoptical axis direction or a slim imaging apparatus, and moving the shakecorrection lens group or the imaging element in the directionperpendicular to the vertical optical axis allows hand-shake correction.Furthermore, a holding force may not be specially required forsupporting the shake correction lens group or the imaging element in thegravitational direction, allowing decreased power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lens block diagram showing a first embodiment of a lightpath folding optical system in an imaging lens device according to anembodiment of the invention;

FIG. 2 shows aberration diagrams for a numerical example 1 derived byapplying specific values to the first embodiment of the light pathfolding optical system together with FIGS. 3 and 4, showing sphericalaberration, astigmatism and distortion at the wide-angle side;

FIG. 3 shows spherical aberration, astigmatism and distortion at anintermediate focal length position;

FIG. 4 shows spherical aberration, astigmatism and distortion at thetelescopic side;

FIG. 5 is a lens block diagram showing a second embodiment of a lightpath folding optical system in an imaging lens device according to anembodiment of the invention;

FIG. 6 shows spherical aberration, astigmatism and distortion for anumerical example 2 derived by applying specific values to the secondembodiment of the light path folding optical system;

FIG. 7 is a block diagram showing an imaging apparatus according to anembodiment of the invention;

FIG. 8 shows one example of drive means for moving the shake correctionlens (group) together with FIG. 9; and

FIG. 9 is a perspective exploded view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Best modes for carrying out the imaging lens device and imagingapparatus according to an embodiment of the invention will be describedbelow with reference to the accompanying drawings.

The imaging lens device according to an embodiment of the inventionincludes a light path folding optical system having a reflector thatfolds the optical axis incident perpendicular to the gravitationaldirection toward the gravitational direction, and an imaging elementthat converts an image formed by the light path folding optical systeminto an electrical signal.

The imaging lens device also includes drive means for moving some oflens groups or one lens (hereinafter referred to as “shake correctionlens group”), or the imaging element in the direction perpendicular tothe optical axis folded toward the gravitational direction by thereflector (hereinafter referred to as “vertical optical axis”). Theimaging lens device is configured such that the shake correction lensgroup or the imaging element is moved in the direction perpendicular tothe vertical optical axis to cancel image-shake that would be generateddue to shake of the imaging lens device. For example, the imaging lensdevice is disposed in the imaging apparatus such that light flux entersthe folding optical system from the direction perpendicular to thegravitational direction during normal use of the imaging apparatus.

Since the imaging lens device according to the embodiment of theinvention has the reflector that folds the optical axis incidentperpendicular to the gravitational direction toward the gravitationaldirection and the drive means that moves the shake correction lens groupor imaging element in the direction perpendicular to the folded opticalaxis that is situated between the reflector and the imaging element(vertical optical axis), the size of the imaging lens device in thedepth direction or the incoming optical axis direction can be reduced,resulting in a slim imaging lens device. For example, the imaging lensdevice is disposed in the imaging apparatus in such a manner that theoptical axis of light flux entering the folding optical system from thedirection perpendicular to the gravitational direction during normal useof the imaging apparatus is folded toward the gravitational directionand the shake correction lens group or the imaging element is moved inthe direction perpendicular to the vertical optical axis to cancelimage-shake that would be generated due to shake of the imaging lensdevice.

Furthermore, as the optical axis incident perpendicular to thegravitational direction is folded toward the gravitational direction andthe imaging element is placed at a position along the folded opticalaxis, the shorter side of the imaging element is oriented to thedirection that determines the thickness of the imaging lens device andhence the thickness of the imaging apparatus incorporating the imaginglens device, thereby providing a slimmer imaging apparatus.

Moreover, since the imaging lens device has the drive means that movesthe shake correction lens group or the imaging element in the directionperpendicular to the folded optical axis that is situated between thereflector and the imaging element (vertical optical axis), and the shakecorrection lens group or the imaging element is oriented in thedirection perpendicular to the gravitational direction in an ordinaryimaging situation in which the incoming optical axis is orientedapproximately in the horizontal direction, the driving force for holdingthe shake correction lens group or the imaging element against thegravitational force may not be always required, allowing substantiallydecreased power consumption. To drive the shake correction lens group orthe imaging element, the gravitational effect may not be required to betaken into account either in the pitch direction (longitudinal directionof the screen) or the yaw direction (lateral direction of the screen).Therefore, the drive means can be the same configuration independent ofthe driving direction, as is the drive control. Even in an imagingsituation in which the incoming optical axis is inclined somewhat upwardor downward from the optical axis in the ordinary imaging situation, asthe gravitational effect on the shake correction lens group is small, asmall driving force will be enough to hold the shake correction lensgroup.

In an imaging lens device according to an embodiment of the invention,it is advantageous that the drive means mechanically bears the weight ofthe shake correction lens group in the gravitational direction. In thisway, the driving force for holding the shake correction lens group orthe imaging element against the gravitational force may not be alwaysrequired, allowing substantially decreased power consumption. Thegravitational effect may not be required to be taken into account ineither the pitch or yaw direction, allowing the drive means to be thesame configuration independent of the driving direction as well as thedrive control to be performed in the same way.

In an imaging lens device according to an embodiment of the invention,the light path folding optical system includes a plurality of lensgroups and works as a zoom lens system in which its magnificationchanges when the respective distances between the lens groups change.The reflector is advantageously placed in a stationary lens group duringzooming. This arrangement allows the shake correction lens group or theimaging element to be oriented perpendicular to the gravitationaldirection as well as a slim imaging lens device in the incoming opticalaxis direction. This arrangement also allows a compact imaging lensdevice because the lens group accommodating the reflector, which tendsto be large, is stationary.

In an imaging lens device according to an embodiment of the invention,it is advantageous to configure the drive means such that no holdingelectrical power may be required to hold the shake correction lens groupaligned with the vertical optical axis. In this way, even when theimaging apparatus is set such that the hand-shake correction function isturned off, or when the imaging apparatus is rotated and heldvertically, or when the imaging lens device is pointed in thegravitational or anti-gravitational direction, the driving force forholding the shake correction lens group or the imaging element may notbe always required, allowing substantially decreased power consumption.Examples of the mechanism that may not require holding electrical powerinclude those using, for example, a stepper motor, DC motor, orpiezoelectric element.

When the shake correction lens group is used as means for correctinghand-shake, the shake correction lens group is desirably fixed in thevertical optical axis direction. Even when the light path foldingoptical system is a variable power optical system, the shake correctionlens group fixed in the axial direction allows slim drive means. Inparticular, if not only drive means for moving the shake correction lensgroup in the direction perpendicular to the optical axis but also amechanism for moving the same in the optical axis direction are togetherincorporated, the size of the driving mechanism for the shake correctionlens group increases in the depth direction or the radial direction anda slim imaging lens device cannot be achieved.

When the shake correction lens group is used as means for correctinghand-shake, the shake correction lens group is desirably fixed in thevertical optical axis direction. In this way, there may be no need toprovide another drive means, that is, means for moving the shakecorrection lens group in the optical axis direction, in the proximity ofthe above-mentioned drive means, thereby preventing an increaseddiameter of the lens barrel.

When the shake correction lens group is used as means for correctinghand-shake, the shake correction lens group is desirably all or part ofa lens group located closest to the imaging element and satisfies thefollowing condition equation (1):|(1−βa)×βb|<1.8   (1)where

βa is the magnification of the shake correction lens group, and

βb is the magnification of the lens group located next to the shakecorrection lens group and closer to the image plane.

When the condition (1) is satisfied, it is possible to correcthand-shake by shifting the shake correction lens group by a small amountwithout having to achieve high precision in positioning in the verticaloptical axis direction. In particular, for digital still cameras and thelike in which the distance between pixels of the imaging element is verysmall and high precision positioning is desired, it is more preferableto satisfy 0.4<|(1−βa)×βb|<1.2.

When the shake correction lens group is used as means for correctinghand-shake, a desirable configuration is the following: the light pathfolding optical system includes, in order of increasing distance from anobject, a first lens group that has positive power and is stationaryduring zooming, a second lens group having negative power, a third lensgroup having positive power, a fourth lens group having positive power,and a fifth lens group having negative power. Zooming is performed bymoving at least the second and fourth lens groups. The first lens groupincludes, in order of increasing distance from an object, a first singlelens having negative power, a reflector that folds the optical axisincident perpendicular to the gravitational direction by 90 degreestoward the gravitational direction, and at least one second lens havingpositive power. The fifth lens group includes a positive lens group asthe shake correction lens group. By configuring as above, compact designand high performance can be achieved. As the second and fourth lensgroups are movable and the third lens group is sensitive to eccentricitydue to manufacturing error, they are not suitable for the shakecorrection lens group. Accordingly, the positive lens group in the fifthlens group having negative power is used as the shake correction lensgroup to achieve a light path folding optical system in whichperformance of hand-shake correction can be substantially consistent.

Examples of the reflector that changes by reflection the direction ofthe optical axis from the horizontal direction to the gravitationaldirection include a prism, mirror or free curved surface lens. Toachieve compact design, a prism is preferably used. By shaping a prismto have a free curved surface, more compact design and higherperformance can be achieved.

In the imaging lens device according to an embodiment of the invention,to achieve a slimmer size thereof, the shake correction lens group orthe imaging element is preferably configured such that its movableranges in the pitch and yaw directions are different. In particular, bysetting the ratio of the travel in the pitch direction to that in theyaw direction within 0.5 to 1.0, the hand-shake correction mechanismcontaining drive means for the pitch direction (the longitudinaldirection of the screen or the direction involved in thicknessreduction) may be more compact.

Embodiments of a light path folding optical system of an imaging lensdevice according to an embodiment of the invention and numericalexamples derived by applying specific numbers to the embodiments will bedescribed.

FIG. 1 is a lens block diagram showing a first embodiment 1 of the lightpath folding optical system. The light path folding optical system 1includes, in order of increasing distance from an object, a first lensgroup having positive power GR1, a second lens group having negativepower GR2, a third lens group having positive power GR3, a fourth lensgroup having positive power GR4, and a fifth lens group having negativepower GR5. The light path folding optical system 1 is a zoom lens inwhich the first lens group GR1, the third lens group GR3, and the fifthlens group GR5 are stationary in the optical axis direction and zoomingis performed by moving the second and fourth lens groups GR2 and GR4 inthe optical axis direction.

The first lens group GR1 includes a negative lens G1, a rectangularprism G2 that folds the optical axis Xh incident perpendicular to thegravitational direction by 90 degrees toward the gravitationaldirection, and a positive lens G3 having an aspheric surface on bothsides. The second lens group GR2 includes a negative lens G4 and adoublet lens G5 formed of positive and negative lenses. The third lensgroup GR3 includes a positive lens G6 with an aspheric surface on bothsides. The fourth lens group GR4 includes a doublet lens G7 formed of apositive lens with an aspheric surface on the object side and a negativelens. The fifth lens group GR5 includes a negative lens G8 and apositive lens G9. The positive lens G9 in the fifth lens group GR5 isshifted in the direction perpendicular to the folded optical axis(vertical optical axis) Xg to shift the image in the directionperpendicular to the vertical optical axis Xg. An aperture stop S islocated close to the image-side surface of the third lens group GR3 andstationary during zooming. A lowpass filter LPF is inserted between thefifth lens group GR5 and the image plane IMG. In FIG. 1, the arrow inthe width direction of the page represents the pitch (Pit) direction,and the arrow in the direction perpendicular to the page represents theyaw (Yaw) direction, and the downward arrow on the page represents thegravitational direction.

The table 1 below shows specification values of a numerical example 1derived by applying specific values to the light path folding opticalsystem 1 according to the first embodiment. In the specification valuetables of the numerical example 1 and the following numerical examplesdescribed later, the “surface number” denotes the i-th surface from theobject. Symbol R denotes the radius of curvature of the i-th opticalsurface. Symbol d denotes the axial distance between the i-th opticalsurface and (i+1)-th optical surface from the object. Symbol nd denotesthe refractive index at the d-line (λ=587.6 nm) of the glass materialhaving the i-th optical surface on the object side. Symbol νd denotesthe Abbe number at d-line of the glass material having the i-th opticalsurface on the object side. Symbols INFINITY, REF and ASP denote thatthe surface in question is a planar surface, reflective surface andaspheric surface, respectively. The shape of an aspheric surface isexpressed by the following equation 1, where x is the axial distancefrom the lens apex, y is the height in the direction perpendicular tothe optical axis, c is the paraxial curvature at the lens apex, K is theConic constant, and A^(i) is the i-th order aspheric surfacecoefficient.

[Equation 1]

TABLE 1 surface number R d nd vd  1: 37.313 0.650 1.92286 20.884  2:8.648 1.380  3: INFINITY 6.900 1.83500 42.984  4: INFINITY 0.200  5:11.744(ASP) 1.988 1.76802 49.300  6: −18.325(ASP) d6  7: 24.918 0.5001.88300 40.805  8: 6.216 1.048  9: −7.984 0.500 1.80420 46.503 10: 8.7151.049 1.92286 20.884 11: 60.123 d11 12: 10.486(ASP) 1.488 1.77377 47.20013: −37.305(ASP) 0.960 14: stop d14 15: 13.0477(ASP) 2.086 1.6667248.297 16: −5.584 0.500 1.90366 31.310 17: −12.676 d17 18: 34.016 0.5001.84666 23.785 19: 6.234 1.187 20: 10.281 1.785 1.48749 70.441 21:−37.764 6.641 22: INFINITY 1.600 1.51680 64.198 23: INFINITY 1.065 24:INFINITY 0.500 1.51680 64.198 25: INFINITY

In the light path folding optical system 1, when the positional layoutof the lenses changes from the wide-angle side to the telescopic side,the distance d6 between the first lens group GR1 and second lens groupGR2, the distance d11 between the second lens group GR2 and third lensgroup GR3, the distance d14 between the aperture stop S and fourth lensgroup GR4, and the distance d17 between the fourth lens group GR4 andfifth lens group GR5 change. Table 2 shows the above distances at thewide-angle side, at an intermediate focal length position between thewide-angle side and the telescopic side, and at the telescopic side forthe numerical example 1, together with the focal lengths f, F numbersFNo. and half angles of view ω.

TABLE 2 FNo. = 3.60 - 3.88 - 4.63 f = 6.52 - 10.95 - 18.54 ω = 30.54 -18.29 - 10.86 d6 = 0.500 - 3.544 - 5.564 d11 = 5.564 - 2.520 - 0.500 d14= 7.525 - 4.851 - 1.882 d17 = 1.300 - 3.974 - 6.943

In the light path folding optical system 1, the both surfaces S5 and S6of the positive lens G3 in the first lens group GR1, the both surfacesS12 and S13 of the positive lens G6 that forms the third lens group GR3,and the object side surface S15 of the fourth lens group GR4 areaspheric surfaces. Table 3 shows the fourth, sixth, eighth and tenthorder aspheric surface coefficients of the above aspheric surfaces forthe numerical example 1, together with the Conic constants K. In Table 3and the table below showing aspheric surface coefficients, “E-i” denotesthe base 10 exponential notation and thus represents “10^(−i)”. Forexample, “0.12345E-05”represents “0.12345×10⁻⁵.”

TABLE 3 surface number K A⁴ A⁶ A⁸ A¹⁰ 5 1 −0.128629E−03 −0.682694E−050.467326E−06 −0.321073E−07 6 1 −0.262565E−04 −0.376614E−05 0.217917E−06−0.236060E−07 12 1 0.628194E−03 0.297806E−04 0.294596E−05 0.847943E−0713 1 0.944369E−03 0.454797E−04 0.140106E−05 0.321119E−06 15 1−0.603083E−04 0.427956E−05 −0.117877E−06 0.644946E−08

FIGS. 2 to 4 are aberration diagrams for the numerical example 1 whenthe light path folding optical system is focused at infinity, and set atthe wide-angle position (f=6.52), at an intermediate focal lengthposition (f=3.88), and at the telescopic position (f=18.54),respectively.

In the aberration diagrams of FIGS. 2 to 4, for spherical aberration,the ordinate represents the ratio of the spherical aberration to thefull-aperture F number and the abscissa represents defocus, where thesolid line represents spherical aberration for d-line, the alternatelong and short dashed line for C-line, and the dotted line for g-line.For astigmatism, the ordinate represents image height and the abscissarepresents focus, where the solid line represents astigmatism for thesagittal image plane and the dashed line for the meridional image plane.For distortion, the ordinate represents image height and the abscissarepresents percentage.

FIG. 5 is a lens block diagram showing a second embodiment 2 of a lightpath folding optical system in an imaging lens device according to anembodiment of the invention. The light path folding optical system 2includes, in order of increasing distance from an object, a plasticprism PP that has an aspheric surface on the object side having negativepower and folds the optical axis Xh incident perpendicular to thegravitational direction by 90 degrees toward the gravitationaldirection, a positive plastic lens G1 having an aspheric surface on theobject side, a negative plastic lens G2 having an aspheric surface onboth sides, and a positive plastic lens G3 having an aspheric surface onboth sides. The positive plastic lens G3 that is situated closest to theimage plane and has an aspheric surface on both sides is shifted in thedirection perpendicular to the folded optical axis (vertical opticalaxis) Xg to shift the image in the direction perpendicular to thevertical optical axis Xg. An aperture stop S is located between theplastic prism PP and the positive plastic lens G1. A lowpass filter LPFis inserted between the final lens G3 and the image plane IMG. In FIG.5, the arrow in the width direction of the page represents the pitch(Pit) direction, and the arrow in the direction perpendicular to thepage represents the yaw (Yaw) direction, and the downward arrow on thepage represents the gravitational direction.

The table 4 shows specification values of a numerical example 2 derivedby applying specific values to the second embodiment 2.

TABLE 4 surface number R D Nd Vd 1 −4.754 ASP 2.900 1.5300 55.844 2INFINITY REF 2.900 3 −11.245 1.000 stop INFINITY 0.700 5 3.561 ASP 2.6341.5830 59.500 6 −3.834 0.650 7 −2.404 ASP 0.850 1.5830 30.000 8 5.524ASP 1.031 9 7.150 ASP 1.733 1.5300 55.844 10 −3.698 ASP 2.103 11INFINITY 0.500 1.5168 64.200 12 INFINITY 0.500 i INFINITY 0.000

Table 5 shows the focal length f, F number Fno. and half angle of view ωfor the numerical example 2.

TABLE 5 f 4.68 Fno. 2.82 ω 32.25

In the light path folding optical system 2, the object side surface S1of the plastic prism PP, the object side surface S5 of the positiveplastic lens G1, the both sides S7 and S8 of the negative plastic lensG2, and the both sides S9 and S10 of the positive plastic lens G3 areaspheric surfaces. Table 6 shows the fourth, sixth, eighth and tenthorder aspheric surface coefficients of the above aspheric surfaces forthe numerical example 2, together with the Conic constants K.

TABLE 6 surface number K A⁴ A⁶ A⁸ A¹⁰ 1 0.000E+00 3.165E−03 −4.400E−056.727E−07 7.529E−08 5 0.000E+00 −4.635E−03 −5.385E−05 −2.888E−044.322E−05 7 0.000E+00 1.720E−02 2.153E−03 0.000E+00 0.000E+00 80.000E+00 3.278E−03 2.266E−03 −5.217E−04 6.296E−05 9 0.000E+00−2.953E−03 1.835E−03 −2.051E−04 6.621E−06 10 0.000E+00 9.940E−032.285E−04 2.208E−04 −2.395E−05

FIG. 6 shows aberration diagrams for the numerical example 2 when thelight path folding optical system is focused at infinity. For sphericalaberration, the ordinate represents the ratio of the sphericalaberration to the full-aperture F number and the abscissa representsdefocus, where the solid line represents spherical aberration ford-line, the alternate long and short dashed line for C-line, and thedotted line for g-line. For astigmatism, the ordinate represents imageheight and the abscissa represents focus, where the solid linerepresents astigmatism for the sagittal image plane and the dashed linefor the meridional image plane. For distortion, the ordinate representsimage height and the abscissa represents percentage.

Table 7 shows values for evaluating the lens condition equation (1)shown in each of the numerical examples 1 and 2.

TABLE 7 numerical example 1 numerical example 2 f 6.52 10.95 18.54 4.68|(1 − βa) × βb| 0.69 0.69 0.69 0.69

As clearly indicated in the tables (Tables 1 to 7), the lenses shown inthe numerical examples 1 and 2 satisfy the condition equation (1). Also,as shown in the aberration diagrams, each aberration is well correctedat the wide-angle side, intermediate focal length position between thewide-angle and telescopic sides, and at the telescopic side.

FIG. 7 shows an embodiment of the imaging apparatus according to anembodiment of the invention. The imaging apparatus 10 includes a lightpath folding optical system 20, an imaging element 30 for converting anoptical image formed by the light path folding optical system 20 into anelectrical signal, an imaging lens device 40 having drive means formoving a shake correction lens group Lc in the direction perpendicularto the vertical optical axis Xg. The imaging element may be an CCD(Charge Coupled Device) or CMOS (Complementary Metal-OxideSemiconductor) type optoelectronic conversion element. The light pathfolding optical system 20 may be a folding optical system according toan embodiment of the invention. FIG. 7 shows the light path foldingoptical system 1 according to the first embodiment shown in FIG. 1, buteach lens group is represented by a single lens in a simplified manner.Of course, besides the light path folding optical system 1 according tothe first embodiment, the light path folding optical system 2 accordingto the second embodiment or light path folding optical systems accordingto other embodiments of the invention other than those shown herein maybe used.

An image separation circuit 50 divides the electrical signal formed bythe imaging element 30 into a focus control signal and an image signal,and sends them to a control circuit 60 and an image processing circuit,respectively. The signal sent to the image processing circuit isprocessed into a form suitable for subsequent processing and undergoesvarious processing, for example, displaying on a display device,recording on a recording medium, and forwarding over communicationmeans.

The control circuit 60 receives external operation signals, such as azoom button operation, and performs various processing in response tothe operation signals. For example, when a zooming instruction isinputted from the zoom button, the control circuit 60 actuates driveunits 71 and 81 via driver circuits 70 and 80 to move the second andfourth lens groups GR2 and GR4 to predetermined positions. Positionalinformation on the second and fourth lens groups GR2 and GR4 detected bysensors 72 and 82 is inputted to the control circuit 60 and referredwhen the control circuit 60 outputs instruction signals to the drivercircuits 70 and 80. The control circuit 60 also checks the focus statusbased on the signal sent from the image separation circuit 50 andcontrols, for example, the fourth lens group GR4 via the driver circuit80 such that the best focus status is achieved.

The control circuit 60 also receives a signal from hand-shake detectionmeans 90, such as a gyroscopic sensor, for detecting shake of the bodyof the imaging element 30 and calculates a shake angle for compensatingfor the hand-shake. To move the shake correction lens group Lc to aposition corresponding to the calculated shake angle, the controlcircuit 60 actuates a drive unit 101 via a driver circuit 100 (thedriver circuit 100 and the control circuit 60 form hand-shake correctioncontrol means). Consequently, the shake correction lens group Lc ismoved to a predetermined position to prevent the imaging position of theobject image formed by the light path folding optical system 20 fromdeviating. Positional information on the shake correction lens group Lcobtained from a sensor 102 is inputted to the control circuit 60 andreferred when the control circuit 60 outputs an instruction signal tothe driver circuit 100.

The above imaging apparatus 10 may take various forms when it is appliedto a specific product. For example, the imaging apparatus 10 has a widerange of applications as a camera unit for digital input/outputequipment, such as digital still cameras, digital video camcorders,mobile phones with a built-in camera, PDAs (Personal Digital Assistants)with a built-in camera. FIGS. 8 and 9 show one example of drive meansfor moving the shake correction lens group Lc in the directionperpendicular to the vertical optical axis direction.

The shake correction lens group Lc is moved by a double-axis actuator200 with a built-in linear motor as drive means in two axial directions,that is, the pitch direction (the direction indicated by the arrow Pitin FIG. 8) and the yaw direction (the, direction indicated by the arrowYaw in FIG. 8).

The double-axis actuator 200 includes a first movable frame 220 that ismovably supported in the pitch direction on a stationary base 210 and asecond movable frame 230 that is movably supported in the yaw directionon a first movement frame 220.

The stationary base 210, when viewed in the vertical optical axisdirection, is a rectangular member with its longer side aligned withsubstantially in the yaw direction and includes a movable frame support211 and a motor mount 212 such that they are integrally connected in theyaw direction. A circular light projecting window 213 is formed in thecenter of the movable frame support 211. Guide shafts 214 and 215extending in the pitch direction are supported on the upper surface ofthe movable frame support 211 on the opposite sides of the lightprojecting window 213 in the yaw direction.

The first movable frame 220 is a rectangular plate-like member with itsslightly longer side aligned with the yaw direction such that itsubstantially covers the movable frame support 211 of the stationarybase 210. The first movable frame 220 is provided with a lightprojecting window 221 at a position substantially corresponding to thelight projecting window 213 of the stationary base 210. Two downwardlyprojecting supports 222 (in FIGS. 8 and 9, only one of them located onthe front side is shown) are formed on the first movable frame 220,specifically, along the pitch direction on both edges of the right endof the first movable frame 220. Each support 222 has a support hole 222a formed therein. Regarding orientation with respect to the double-axisactuator 200, the right and left directions and up and down directionsare the same as those in FIGS. 8 and 9, and the frontward and rearwarddirections correspond to the directions toward and away from the reader,respectively. A guide projection 223 is formed on the underside of theleft edge of the first movable frame 220, and an engagement cutout 223 athat is open on the left side is formed in the guide projection 223. Twosupport projections 224 are formed on the upper surface of the firstmovable frame 220, specifically, on left and right edges on the rearside of the upper surface. A guide shaft 225 is supported between thetwo support projections 224. Two support projections 226 are formed onthe upper surface of the first movable frame 220, specifically, one atthe right edge of the front side of the upper surface and the other at aposition slightly to the left thereof. A guide shaft 227 is supportedbetween the two support projections 226.

The two support holes 222 a of the two supports 222 formed on the rightedge of the first movable frame 220 receive the guide shaft 214 on theright side of the stationary base 210 such that the portions close tothe ends of the guide shaft 214 are slidably inserted in the two supportholes 222 a. The engagement cutout 223 a of the guide projections 223 atthe left end of the first movable frame 220 slidably engages the guideshaft 215 on the left side of the stationary base 210. In this way, thefirst movable frame 220 is movably supported in the pitch direction onthe upper surface of the stationary base 210.

A second movable frame 230 includes a lens support 231 and a magnetsupport 232 to the right thereof such that they are integrallyconnected. The lens support 231, when viewed as a plan view, is arectangular member with its longer side aligned with the yaw directionand has a size slightly smaller than the first movable frame 220. Thelens support 231 has a track-like lens support hole 233 with its longerside aligned with the yaw direction, in which the shake correction lensgroup Lc is supported. A long block-like support projection 234 with itslonger side aligned with the yaw direction is formed on the rear edge ofthe second movable frame 230. The support projection 234 has a slidehole 234 a formed therethrough in the yaw direction. A frontwardlyprojecting guide 235 is formed on the right end on the front side of thelens support 231, and an engagement cutout 235 a that is open on thefront side is formed in the guide 235. The magnet support 232 is locatedslightly above the lens support 231 and is connected with the lenssupport 231 by a stepped portion 236 therebetween.

The guide shaft 225 of the first movable frame 220 is slidably insertedin the slide holes 234 a in the support projection 234 of the secondmovable frame 230. The engagement cutout 235 a of the guide 235 of thesecond movable frame 230 slidably engages the guide shaft 227 of thefirst movable frame 220. In this way, the second movable frame 230 ismovably supported in the yaw direction on first movable frame 220.

A linear motor 240 includes a stator coil 250 and a moving magnet 260.

The stator coil 250 has a voice coil 251 and a flat coil 252. The voicecoil 251 is configured such that a coil wire is wound to form a tubularshape with its axial direction aligned with the pitch direction. Theflat coil 252 has large and small coils 252 a and 252 b arranged side byside in the yaw direction, each coil being wound to form a track-likeshape with the longer side aligned with the pitch direction. Electricityis fed into the two coils 251 and 252 through a flexible print board253, which is supported by a backing plate 254. The voice coil 251 issupported on the underside of the flexible print board 253 and the flatcoil 252 is supported on the top of the backing plate 254. A supportmount 255 supports the backing plate 254 to form the stator coil 250.The stator coil 250 is placed on a motor placement portion 212 of thestationary base 210 by fixing the support mount 255 of the stator coil250 on the upper surface of the motor placement portion 212 of thestationary base 210.

The moving magnet 260 includes a back yoke 261 and two magnets 262 and263. The back yoke 261 is formed of two planar rectangular yoke pieces261 a and 261 b with their longer sides aligned with the pitch directionsuch that the upper and lower yoke pieces 261 a and 261 b are placedparallel, facing each other, and integrally connected by a connectingpiece 261 c at their rear left ends. The magnet 262 is fixed on theunderside of the upper yoke piece 261 a and the magnet 263 is fixed onthe upper side of the lower yoke piece 261 b, thereby forming the movingmagnet 260. The upper side of the upper yoke piece 261 a is supported onthe underside of the magnet support 232 of the second movable frame 230and the left side of the connecting piece 261 c is supported on theright side of the stepped portion 236 of the second movable frame 230,thereby supporting the moving coil 260 on the second movable frame 230.The lower yoke piece 261 b and the magnet 263 are inserted in the voicecoil 251 of the stator coil 250 such that the lower yoke piece 261 b andthe magnet 263 are movable in the pitch and yaw directions, and theupper magnet 262 is placed over the flat coil 252, facing each other,with a small gap therebetween.

When the voice coil 251 of the double-axis actuator 200 is energized, amoving force in the pitch direction acts on the moving magnet 260. Themoving force is transferred to the first movable frame 220 via thesecond movable frame 230 and the first movable frame 220 is moved in thepitch direction along the guide shafts 214 and 215 of the stationarybase 210. Consequently, the second movable frame 230 supported on thefirst movable frame 220 moves in the pitch direction and hence the shakecorrection lens Lc supported in the second movable frame 230 moves inthe pitch direction. When the flat coil 252 is energized, a moving forcein the yaw direction acts on the moving magnet 260. The moving force istransferred to the second movable frame 230, which is then moved in theyaw direction along the guide shafts 225 and 227 of first movable frame220. Consequently, the shake correction lens Lc supported in the secondmovable frame 230 moves in the yaw direction.

As described above, by selecting the direction and the amount of thecurrent applied to the voice coil 251 and/or the flat coil 252 asappropriate in the double-axis actuator 200, the shake correction lensLc can be moved in all directions perpendicular to the vertical opticalaxis Xg by a desired amount. In the double-axis actuator 200, since themovable portion including the shake correction lens Lc is supported inthe gravitational direction on the stationary base 210, coils 251 and252 may not be required to be energized except when the shake correctionlens Lc may be required to move. Even when the attitude of the imagingapparatus and hence the imaging lens device inclines to a certainextent, the shake correction lens Lc can be held in a desired positionwith a small current. In particular, since the moving magnet 260 has themagnets 262 and 263, unless the coils 251 and 252 are energized, themoving magnet 260 is positioned at a neutral position where theresultant attractive force of the magnets 262 and 263 is in a stablestate. By setting the neutral position to a position where the center ofthe shake correction lens Lc coincides with the vertical optical axis,the coil 250 may require very little current flowing therein when thehand-shake correction function is not activated.

In the double-axis actuator 200, since the double-axis drive unit forthe pitch and yaw directions, that is, the linear motor 240 is placedall together on one end in the yaw direction, the size in the yawdirection becomes larger, while the size in the pitch direction (thedepth direction of the imaging apparatus) can be minimized to the extentthat may be required for supporting the shake correction lens Lc movablein the two directions. This means that the presence of the double-axisactuator 200 does not prevent a slim imaging lens device and imagingapparatus.

Of course, it is not intended that the drive means of the shakecorrection lens (group) in the invention is limited to the double-axisactuator 200 described above.

Specific shapes and structures as well as numerical values of theportions shown in the above embodiments and numerical examples are byway of example only to embody the invention and should not be construedas limiting the technical range of the invention.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An imaging lens device comprising: a light path folding opticalsystem having a reflector that folds the optical axis incidentperpendicular to the gravitational direction toward the gravitationaldirection; an imaging element that converts an image formed by the lightpath folding optical system into an electrical signal; and a drive unitthat moves a shake correction lens group including at least one lens inthe direction perpendicular to a vertical optical axis, the verticaloptical axis being folded toward the gravitational direction by thereflector, wherein the shake correction lens group is moved in thedirection perpendicular to the vertical optical axis to move the imagein the direction perpendicular to the vertical optical axis.
 2. Theimaging lens device according to claim 1, wherein the drive unitmechanically bears the weight of the shake correction lens group in thegravitational direction.
 3. The imaging lens device according to claim1, wherein the shake correction lens group is fixed in the verticaloptical axis direction.
 4. The imaging lens device according to claim 1,wherein the shake correction lens group is all or part of a lens grouplocated closest to the imaging element and satisfies the conditionequation (1)|(1−βa)×βb|<1.8, where βa is the magnification of the shakecorrection lens group and βb is the magnification of the lens grouplocated next to the shake correction lens group and closer to the imageplane.
 5. The imaging lens device according to claim 1, wherein thelight path folding optical system includes a plurality of lens groupsand works as a zoom lens system in which its magnification changes whenthe respective distances between the lens groups change; and thereflector is placed in a stationary lens group during zooming.
 6. Theimaging lens device according to claim 1, wherein the light path foldingoptical system includes, in order of increasing distance from an object,a first lens group that has positive power and is stationary duringzooming, a second lens group having negative power, a third lens grouphaving positive power, a fourth lens group having positive power, and afifth lens group having negative power; zooming is performed by movingat least the second and fourth lens groups; the first lens groupincludes, in order of increasing distance from an object, a first singlelens having negative power, a reflector that folds the optical axisincident perpendicular to the gravitational direction by 90 degreestoward the gravitational direction, and at least one second lens havingpositive power; and a positive lens group in the fifth lens group is theshake correction lens group.
 7. The imaging lens device according toclaim 1, wherein the mechanism of the drive unit may not require anyholding electrical power for holding the shake correction lens groupaligned with the vertical optical axis.
 8. An imaging lens devicecomprising: a light path folding optical system having a reflector thatfolds the optical axis incident perpendicular to the gravitationaldirection toward the gravitational direction; an imaging element thatconverts an image formed by the light path folding optical system intoan electrical signal; and drive unit that moves the imaging element inthe direction perpendicular to a vertical optical axis, the verticaloptical axis being folded toward the gravitational direction by thereflector.
 9. The imaging lens device according to claim 8, wherein thedrive unit mechanically bears the weight of the imaging element in thegravitational direction.
 10. The imaging lens device according to claim8, wherein the light path folding optical system includes a plurality oflens groups and works as a zoom lens system in which its magnificationchanges when the respective distances between the lens groups change;and the reflector is placed in a stationary lens group during zooming.11. The imaging lens device according to claim 8, wherein the mechanismof the drive unit may not require any holding electrical power forholding the shake correction lens group aligned with the verticaloptical axis.
 12. An imaging apparatus comprising: an imaging lensdevice having a light path folding optical system and an imaging elementthat converts an image formed by the light path folding optical systeminto an electrical signal; a hand-shake detector that detects shake ofthe imaging lens device; and a hand-shake correction controller thatcorrects displacement of the imaging position of the object image basedon the shake of the imaging lens device detected by the hand-shakedetector, the imaging lens device including a reflector that folds theoptical axis incident perpendicular to the gravitational directiontoward the gravitational direction, and a drive unit that moves a shakecorrection lens group including at least one lens in the directionperpendicular to a vertical optical axis, the vertical optical axisbeing folded toward the gravitational direction by the reflector,wherein the imaging lens device is configured such that the shakecorrection lens group is moved in the direction perpendicular to thevertical optical axis to move the image in the direction perpendicularto the vertical optical axis; and the hand-shake correction controllerinstructs the drive unit to move the shake correction lens group by anamount and in a direction based on the shake of the imaging lens devicedetected by the hand-shake detector.
 13. An imaging apparatuscomprising: an imaging lens device having a light path folding opticalsystem and an imaging element that converts an image formed by the lightpath folding optical system into an electrical signal; hand-shakedetector that detects shake of the imaging lens device; and hand-shakecorrection controller that corrects displacement of the imaging positionof the object image based on the shake of the imaging lens devicedetected by the hand-shake detector, the imaging lens device including areflector that folds the optical axis incident perpendicular to thegravitational direction toward the gravitational direction, and a driveunit for moving the imaging element in the direction perpendicular to avertical optical axis, the vertical optical axis being folded toward thegravitational direction by the reflector, wherein the hand-shakecorrection controller instructs the drive unit to move the imagingelement by an amount and in a direction based on the shake of theimaging lens device detected by the hand-shake detector.